In the past, it has been customary to form microwave oven cavities from sheet matal parts. The cavity of the microwave oven was typically made up of such sheet metal into a generally box-shaped structure having one side substantially open for access in inserting and retrieving food when the access door was open. Such sheet metal structures have been relatively expensive and difficult to manufacture. In addition, such structures usually required post-forming treatment such as painting to provide for an aesthetically pleasing interior surface which was at the same time required to be hygienic because microwave ovens are used to prepare food.